This invention relates generally to teat cup assemblies for vacuum-operated milking machines including a rigid shell and a flexible liner, and in particular to an apparatus for installing and/or removing the flexible liner from the shell.
Automatic milking machines employ teat cup assemblies having a hollow, rigid outer shell and a resilient liner (also called an “inflation”) including a tubular body installed within the shell in a manner to form a seal at both ends of the shell. The terms “inflation” and “liner” are used interchangeably in the trade. The shell and liner define an annular chamber there between to which a pulsating vacuum can be applied. The cow's teat is inserted into the upper end of the liner and a milking tube portion on the lower end is connected to a manifold (called a “claw”) of the milking machine. During the milking operation, a pulsator switches on and off to apply a vacuum to the chamber in the teat shell 12 that causes the liner 14 to expand, increasing its internal diameter and relieving pressure on the teat. The pulsator can then vent the chamber to atmosphere and the liner 14 contracts, squeezing the teat to express milk therefrom into the liner.
One type of conventional teat cup assembly 10 is shown in FIGS. 1 and 2 and has a generally cylindrical shell 12 and removable liner 14 (the reference numbers indicating their subjects generally). The shell 12 has a tubular body 15, a lower end 16 including an opening 17 of reduced diameter and an upper end terminating in a rim 18. Located in the side of the shell 12 is an air tube 19 connected via suitable tubing (not shown) in communication with the pulsator which alternately vents to atmosphere and applies a vacuum to an annular chamber between the interior wall of the shell 12 and a portion of the liner 14 inside the shell to alternately squeeze and release the teat to express milk. The shell 12 can be made from a metal, such as stainless steel, or a synthetic thermoplastic or thermosetting material, including transparent or translucent materials so that the milking operation of the liner 14 can be observed.
The liner 14 has an elongated, generally cylindrical suction sleeve or barrel section 20 which fits inside the shell 12 and a head section 22 which has a circular opening 24 for receiving a cow's teat. The head section 22 has a peripheral downwardly extending skirt or cuff 26 which surrounds the rim 18 of the upper end portion of the shell 12. The cuff 26 is spaced radially outwardly from the outer wall of the liner 14 to define an annular recess which receives and sealingly engages the rim 18 of the shell 12. The liner 14 also has a lower section 30 which fits through the opening 17 in the lower end 16 of the shell 12. A sealing ring 28 on the liner 14 is sized to be pulled through the opening 17 and sealingly engage the shell 12 so that the liner is elongated and under tension when assembled within the shell. In this way, the liner 14 seals with the shell 12 at the cuff 26 and the sealing ring 28 and makes the annular chamber airtight. The liner 14 may be a one-piece unit or a multiple-piece unit. The liner 14 can be made from any of a variety of conventional elastomeric materials such as synthetic or natural rubber. The cuff 26 has an upper alignment mark 27 that corresponds to another lower alignment mark 29 directly under the sealing ring 28 on the lower section 30. When installed correctly, mark 27 on the cuff 26 and mark 29 on the lower section 30 must be aligned with each other to avoid twisting. The construction of the teat cup assembly is conventional and may be varied without affecting the scope of the present invention.
During milking operation, the barrel section 20 of the liner 14 is subjected to repeated alternating stretching and releasing by the vacuum system, which eventually breaks down the barrel section 20 and results in an inefficient or incomplete expression of milk. Additionally, the liner 14 is vulnerable to deterioration caused by scalding water, teat treatment preparations, cleaning chemicals, and an accumulation of butterfat. Also the head section 22 and lower section 30 can be subjected to a number of potentially damaging conditions such as flexing when not in use or impacts, e.g., dropping on a concrete floor or drain grating of a milking stall, banging into a milking stall wall, another teat cup assembly 10 or other equipment, or being stepped on by a cow. Any or all of these conditions could result in the downgrading or rejection of the bulk milk due to contamination, as well as unsafe for the health of the cow. Accordingly, it is recommended by all manufacturers of the liner 14 that replacement be routinely scheduled in order to maintain a uniform and efficient operation, maximize milk yield, and provide gentle, fast, and safe milking to preserve udder health.